Thursday, 17 October 2013

Introduction to JavaScript and Introduction to Jscript

Introduction
to JavaScript and Introduction to Jscript

JavaScript in a programming language and it is specifically
made for the web browsers to use. It is used in HTML to create interactivity
between the web pages. There is a very similar language called Jscrpit which is
made by Microsoft. Microsoft has provided a version of Jscript for the desk top
users it means for the local use in a machine and it can be used with the help
of Windows Script Host (WSH).

The Windows Script Host (WSH) is an optional scripting
environment that supplies Windows operating systems with the capability to run
scripts directly on the Windows desktop. Both languages support the same
collection of programming statements.

JavaScript and JScript are interpreted
languages. This means that scripts written in these languages are not compiled
before they are executed (as is typical of most programming languages such asC++). Every script statement must first be converted into binary code (a computer language made up of 0s and 1s
that the computer can understand) in order to execute. Unlike complied
programs, which are converted to binary code in advance, JavaScript and JScript
statements are processed at execution time. This means that they run a little
slower than compiled programs. The upside is that this makes writing and
testing JavaScripts and JScripts very intuitive and easy. You simply write a
few lines of code, save your script, and test it without having to stop and
compile it into executable code.

Both JavaScript and Jscript are object-based scripting
languages not truly object oriented languages. They have almost everything as
object. Everything in JavaScript is an object, for JavaScript a browser, a
window, a button etc are objects. JScript has access to a different set of objects.
For example, JScript has the capability to access objects such as files,
drives, and printers.

Every object has properties,
and you can use JavaScript and JScript to manipulate these properties. For
example, with JavaScript you can change the background color of a browser
window or the size of a graphic image. In addition to properties, objects have
methods. Methods are the actions that objects
can perform. For example, JavaScript can be used to open and close browser
windows. By manipulating their properties and executing methods, you can
control objects and make things happen.

JavaScripts support event-driven
programming. An event
is an action that occurs when the user does something such as click on a button
or moves the pointer over a graphic image. JavaScript enables you to write
scripts that are triggered by events. Did you ever wonder how buttons
dynamically change colors on some Web sites when you move the mouse over them?
It's simply a JavaScript technique known as a rollover.
The event is the mouse moving over the button (object). This triggers the
execution of an event handler, which is a
collection of JavaScript statements that replaces the button with another one
that uses a different color.

JavaScripts and JScripts that run inside Web browsers have
access to objects placed on Web pages. On the other hand, JScripts that run
within the WSH have access to desktop resources such as toolbars, files,
printers, and the Windows registry.